An ultrasonic diagnostic apparatus is a medical equipment for obtaining an ultrasound image of a target region in an object so as to provide clinical information of the target region, such as lesion or neoplasm information of internal organs, fetus information and the like. Typically, the ultrasonic diagnostic apparatus comprises at least one probe for radiating an ultrasonic wave to the target region and receiving an echo signal reflected from the target region. The probe has a transducer for converting an ultrasonic signal into an electric signal.
Recently, in order to obtain more accurate diagnosis, there have been developed techniques for acquiring a 3-dimensional (3D) ultrasound image by pivoting the transducer.
As shown in FIG. 5, Japanese Patent Application Publication No. 2004-290272 discloses a prior art ultrasonic probe with a device for moving a transducer. FIG. 5 is a perspective view showing a device for moving a transducer of a prior art ultrasonic probe.
As shown in the drawing, a prior art probe 1 is equipped with a frame 5 and a cover 8, which is coupled to the frame 5 and is adapted to contact an object to be examined (e.g., a body of a patient). A motor 4 for generating driving power for pivoting a transducer 2 is mounted to the frame 5. A driving arm 6 is fixed to a driving shaft of the motor 4. A holder 3 for supporting the transducer 2 is mounted to the frame 5. The holder 3 has a holding part 3a for holding the transducer 2 and a pair of swing parts 3b, which are coupled to both side-ends of the holding part 3a and mounted pivotably to the frame 5 by hinge pins 9. The holding part 3a of the holder 3 is arranged to confront the driving arm 6 and has a groove (not shown) on the surface facing the driving arm 6. The driving arm 6 has a recess (not shown) on the surface facing the holding part 3a of the holder 3. The recess is located eccentrically with the driving shaft of the motor 4. A ball (not shown) is interposed between the recess of the driving arm 6 and the groove of the holding part 3a. When the motor 4 operates and the driving shaft is rotated, the ball contained in the recess of the driving arm 6 revolves around the driving shaft. At the same time, the ball rolls along the groove of the holding part 3a to thereby pivot the holder 3 holding the transducer 2 on the hinge pins 9.
However, in the above prior art device that moves the transducer of the ultrasonic probe, the rotation angle of the driving shaft of the motor, which is determined by the duration of a pulse, directly influences the pivot angle of the transducer through the driving arm and the holder. Thus, the transducer moves somewhat roughly and the ultrasonic wave is radiated irregularly. As such, the image quality becomes degraded, which can cause an erroneous diagnosis. Although a high-precision motor may be provided in order to resolve this problem, it causes a considerable increase in manufacturing costs.
Also, the radius of rotation of the transducer is determined by the length of the swing part of the holder. Thus, when manufacturing the probe having a relatively large radius of rotation of the transducer, the probe may be enlarged ineffectively or the limited size of the probe may impose many undesired limitations upon installing the long holder.